Sph. Radius: This controls the radius of the volumetric particles. Low value controls how it starts off when it's emitted, the high value controls how it looks like when it ends, and inbetween animates up. The var value gives variation to it, so the size of each particle can vary slightly.

*note* The AFC ramp is helpful if you want the particles to emit REALLY small and then suddenly blast out big or something, you can adjust the ramp to be small and then raise up really quickly. Can be handy at times.

Squash: Squash.. squashes the particles, making them fat and short spheres ect. The values for high low and var are the same as above.

Squash Lenght: This kind of warps the perspective of the shape of the sphere, making grow out from the center, effecting the shading and lighting and surface texture of the particle.

Rotation: This allows you to give 3D rotation coordinates so you can control how the particles rotate over time, you can animate this value via the high and low values.

Type: Here you can make the volumetric particles a sphere, cylinder, box ect. This essentially controls the shape of the particles. Hemisphere, cuts the sphere in half.

Alignment: This by default is off, if you put it on (part. velocity) it will automatically rotate the particles for you based on their velocity.

Autostretch: Based on the motion of the particles it'll stretch the particles out as the move or do any sudden movements, kind of like squash and stretch rules.

Note: There's a box to the right, with a small grey box with a red stripe in it to the bottom right of that, if you click on the red stripe it'll turn on a preview window for this allowing you to have a better visualisation of the look and animation of these parameters.